Method and means for starting synchronous motors



` 1,640,322 Aug' 23 1927 c. T. HIBBARD METHOD AND MEANS Foa STARTING s-YNGHRONQUS MToRs Filed Jan.' 17 1920 OHAEEES TEUMAN YIII-Binnen, OE MINNEAPOLIS, MINNESOTA,l ASSIGNOE, EY MESNE ASSIGNMENTS, To OTEIO MACHINERY MFG. COMPANY, or MINNEAPOLIS,

MINNESOTA; A OORPORATION'OF MINNESOTA.

L METHOD. AND MEANS ronV STARTING SYNCHBONOUS MOTORS. f

l. Application' ined January 17, 1920. seri/atm. 352,159.

'Oneobjvect oiiiny invention is to'provide al method andfmeans for starting synchronous motors from the actuation Ofla push button. Another object is to provide a method and means whereby the motor is *started` auto- 'matically at' a reduced voltage and with no excit'ation current, and whereby when the' motorhas-attained a predetermined percent- 'age-fof synchronousspeed, the full voltage '10 v'will'be" a]g )`plied to the motor, and thereafter "thelfie'ld will .be automatically excited.

" Another v.Object is Tto"provide improved "-,means andmethod for automaticallyexcitting the motor field` a's'the motor approaches- A 15. Synchr-onisrr'1.`

Another Object is-,to provide 7.a method and `-means whereby the field will possess the cori rect polarityv when the-field circuit is closed.

"With these and incidental Objects in view,

29 the invention consists of `certain novel features .ofconstru'ction and Acombination oit parts, the essential elements of whlchgare hereinafter described withV reference-tothe vvpartotthis specification. l ,In the d.1awin,q',Figurc i is a schematic view of arcircuit showing' one embodiment of nlyinventio'n; and Figure 2- is a conventional representation of an oscillogram showing the current induced in the ield winding, as the' motor is started.

' In the .ordinary method for starting syn-- chronous motors `it is customary to throw aA switch whicliwiil connect thermotor-with a tap from the transformer so as to startfthe motor at a reducedvoltage and With noeX- Then the motor has attained a certain. speed a switch is thrown so as to-'bring a' vfull voltage on the motor and' then when the motor has practically reached synchronism,

the field is closed and the -'motor pulls into' One oi the problems of the handling. of synchronous motors. and especially by unskilled help, has been to de viseI means-whereby the full voltage will be thrown onto the` motor at lthe' proper time. 'and anotherstill more important problem' has been to devise means whereby'- the field eXcitatIOn'curret "may be thrownon atithe proper time during'.l

Tdrawingl which accompanies and .forms a stant the .field 1S closed.

Athe `motor is in synchronism.

synchronous speed.

Inas'much as the time required for the nio `tor to attain synchronous speed will vary under load conditions, it is .evident'that no predetermined' interval canv be used for either' applying the Ifull voltage to the motor,

or more especially; for 'applying the excita tion 'currentjat the right instant. It is also apparent that if the field is of the wrong polarity when the field circuit is closedtherewill be a surge in the line cur? rent and the motor will also be 'subjected to heavy mechanical strains, so' the proposi- ,tion that `the ield should be of the right po'- :larity when the' field circuit is closed will be accepted bly everyone skilled in the art.

S0 far as am aware, there havebeen no feasible, automatic means proposed for autoniatical'ly startinga synchronous motor tO meet-the necessary requirements, and to the best of my knowledgano practical means whatever s been suggested for automatically securi'ng the correct polarity atthe 1n- When the voltage from the-low.

transformer is thrown Onto the motora .cur-

rent is induced in the field winding'and this `current is maintained when the full volta'ifeA is applied and vcontinues-at subst-antially`its full `val-ue until the motor is"with infa i l percent of synchronous'speed. e

This lield current is, of'coursealternating, and like` the field voltage,v frequency equal to the slip, decreasing 4from a maximum frequency equal 'to that'I of the 'supply current, until itreaches vzero when Asshown in the Oscillogram 1n 2 when themotoristirstv started the current has a frequency at the point l equal to that of'thesupply current; at the point 2 the' frequency has decreased greatly, while-at the' pointl 3 the frequency is'extremely slow,

and from the point LLito the point 5 the current dies away and at the point 5 it is zero,. A.

theVA this representing theA instant at which motor reaches Synchroniszn. Y In 4mylinethod I utilize this induced field current tO'- det'ermine, first, the point' `,at

hich '1l'A "ne voltage'shouldbe thrown onto the motor; second, to determine posi- 'tively the point at'which the excitation current should/be applied; vand third, I utilize current should be applied, it is nevertheless true thatl in this induced field current we have a means at hand which indicates 1n 1tself the time at which the field excitation current should be applied, and, also the time of the cycle atwhich the application must be made in order that the excitation will be in the proper direction to cause the motor toi pull into synchronism.

Obviously, this induced field current also furnishes the best possible means for determining at what instant the full voltage should be applied to the motor as the fieId current is at all times in definite timed rela-v tion with the speed of-the motor and the frequency of the supply current.

, Inasmuch as the frequencies at the point 2, Figure 2, is greatly reduced below that at the point 1, it is evident that electrical means can be devised that will operate at fref quencies such as that represented at polnt 2,

- and will not operate at frequencies such as that represented at the point-1.

It is also evident that there is a sufficient difference infrequencies between the polnts 2 and 3 to` allow the use of an 'electrical de vice that can be adjusted to function in a certain way under infiuence of frequencies l suoli as .that represented at 3, and not to function in the same manner under influence of frequencies such as that represented at the point 2. f

It'is also obvious that an electrical de vice can be constructed that will actuate for instance, when `this current is above the line, as at 6, but will not. actuate .when the current is below the line, as at 7, so that the field excitation current might be made.

` In other words, either the application of the full voltage or the application of the .ieldexcitation current, or both, may be made to depend absolutely and entirely upon the internalelectrical condition of the field winding itself, through the action of this induced current, l f i In the circuit shown in Figure 1, I have indicated one means by-which this may be accomplished and inthis circuit the -power lines are represented at 8 with the usual trans former 9 and ammeter 10.

In starting the motor the attendant has only to close the circuit by means of the push button lland the motor is brought into synchronism in the proper manner, automatically and without further attention or care on the part of the'attendant, who maybe at a point distant from the motor andnot even see the motor at the time he closes the push button circuit. The push button 11 may be actuated by any automatic device not requiring 'the attention of the operator and at a remote point` such for iin sta-nce as a fioat switch in a water tank or a pressure gauge on a gas tank.

The operation of the push button 11 actuates a `relay or contactor switch 12, the cir-v cuit being as follows: Source ofl current supply 13, wire 14, push button 11, wire 15, winding 16, and wire 17, to the other side of the source of current supply.

Upon the closing of the contact 18 a switch 19 'is thrown to the right, as shown in the sketch, by the actuation of the coil 20, the

circuit being as follows: Power wire 21, wire 22. contact 18, wire 23, coil 20, wire 24, to` power wire 25.

'Ihe switch, when thrown to the right, remains in that position until withdrawn, but the coil 2O is energized only so long as the contact 18 remains closed.

The closing of the switch to the right applies a full voltage of the line to the transformer 2G, thc circuit being as follows: Power lines 25, 21,'and 27, switch 19, wires 28, 29, and 30, to the transformer 26.

Fromthe low voltage taps the current is applied to the motor, the circuit being as follows: Wires 31, 32, 33, wires 34, 35, 36, to the stator 37 of the motor. p

As soon as the current is applied to the stator current is induced` in the rotor` 38 through the followingl circuit: Rotor 38, wire 39, primary 40 of the transformer 41,wire 42, field rheostat 43, wire 44, contact of the switch 46eld discharge resistance 47, wire 49, primary 5() of the transformer 51,

ooA

lull

wire 52, to the other side of the rotor or field 38.

When the motor is first supplied with the current a circuit is established throughthe actuating coil 53 of the switch 19, the circuit being as follows: Vire \35, wire 54, coil 53, Contact 57 of the push button 58, wire 59, thro-ugh the frame of the relay 41', cont-act 60. and wire 61 to the wire 34.- Y

IVhile the coil 53 is energized, at least partially, by this circuit, the switch 19 is not thrown to,the left-by the actuation of the coil 53 as the contact 60 in the circuit energizing the coil 53 isbrokenby the energizing of'the coil/10 hefore the coil53 can affeet theposition of ltheswitch .19.V The relay `41 is energized by the current from i the transformer 41as the secondary 43 is directly connected-tothe winding; .40 ofthe relay 4l. -v

, The frequency relay 41 is. adjustable andis set to release its arinatiirewlien the frequency of its actuating current falls below 4a predetern'iined amount, for instance, that in,

dicated at point 2, Figure 2, the relay being such that it will quickly -respond vto a fre- 4 quency such as that indicated at-1, Figure 2, and release under the lower frequencyas' indicated.

lIt is evident centage of synchronism such that the induced current in the field winding would have a fieqiiency'such as isrepresented at 2, Eigure 2, the frequency relay 41. will he releasedv and the contact 60 closed and this contact 60 will remain closed under decreasingffrequenc'ies.,

Upon the closing' offthe Contact 60 'the coil- 'j 53 is energized and the switch 19 thrown tothe left, thus applying full voltage to the i motor through the yoverload relays 100;

In the fieldcircu'it already traced is in.-

eluded thel primary 50 of the transformer `51 andthe secondary 62 of this transformer is connected directly to the 'winding 63 of the frequency relayv 64, which isadji'istahle and is so adjusted that it will he actuated bya current'of frequencies higher than thatj repre-rented at the point .2, Figure -2, for instance, and will release at a frequency suchasthat vrepresentedat 3, Figure 2.

A. The' frequency .relay 51 was actuatedand' its armature drawn up andjcontact 65 opened at the same instantthat lfrequency relayf41 was actuated, and when its arma-J ture is released as the motor approaches synclironisni and. at such a' pointthatthe.' frequency of the induced iield winding'` is represented at 3, Figure 2, a circuit is established-as follows: .field winding 88, wire' 52 primary, winding 50 of theitransformer 51, wire 49, wire 66', frame of the relay 64, contact 65, Wire 66, winding 67 of the polarized relay 68, wire 69, wi're'44, rheosta-t 4 3, wire l '41 and wire 39 baciatothe field winding'38.

. `rent passing'through the vrela-y is lof proper.

"when the current'is of the 42, primary windingofthe transformer inasmuch as the relay 68 is polarized, prefi- Aera-bly by al permanent magnet, it is evident' vit will respond to pulsations of currentof one direction".only and the :Contact `l70 will he closed only when'the-pol-arity ofthecur'- sign such, for instance, as that" at 6, Figure 2, and that the 'contactvO' wilt be opened as at' 7, Figurev 2. 1';

The closing- 'ofr the contact '70 energizes the coil 71, the" circuitheing aslfollows;

therefor, 'that when the motor has reachedv a certain predetermined per-currentlsupply-.j

- rectly` into synchronism. 1

opposite polarity,

source of field excitation current at 7 2, Wire .the other side .of jithe Source of. ciirrent` supply` l The. energizing ofythecoil` 71 throws the" switcli'46to 'the right, applying the field I cuirent to the'field winding` 3 8 4and cutting out the field discharge resistance 47 Athe field excitation current circuit being asffollowsg source of current supply-7 2, wire 7 3, switc'h. A Y

46, wire 48, wire 49, primary ofthe transformer 51', wire'52, field. Winding 38,'- Wire 39, primary 4() of thetransformer 41, wire` 42, rhe'ostat 43,1wiie544, switch-46,1wires 78 78, tothe other side of the'source of ".Inasmuch as vthe field was excited -hy means of the magnetizingswi'tch at afprefl determined condition of the cycle of thein y ducedl field current,it"is 'evident thatfthe excitation current' would always he^ ,appliedvl inthe proper direction to liftthe motor 'di- The frequency relays, as shown'in the draw` ing, are representative of anytype fofrelay or device that will function in oneinannerunder the influenceof a current of -a-.cerl tain frequency and bel-'disposed in a different vmanner under1 the influence of a cur-'j rent, of fa lower. frequency, and any devicev that will so .function may beiised as va fre`- quen-cy relay. in my method.

The jpolarized'relayis shown in the draw- .rod

ing as a conventional representation of. a

.erated switches are shown as conventionalxUj-v. y -i'epiesentations '.ofswitehes whose operation` is wellknown to alleth'ose skilled in the a1t,`;

and while shown conventionally, 4Iwvisli it understood that'they representoperatire 4 elevknown devices producing a new effect',4 As stated above,l the..l frequency relay. A64 4is 'adaptedfto open thecontact 6ywhen-thefrequency, of the .induced*field-current is Y "l' :higher than that represented. at t he point 2, Fig-2,- for-instance, andto-close tliiscni-y .tact when the frequency is-sueh as that repf -A resented at-'3, Therefore,l if-'th'e motor pulls'i-out of step" forany reason Ithe frequency of jtheinduced: field 'current increasesheyond the .point 25, Figi-2, for'- instance, the `relay-'.64 will operate to' break` the 'circuit including. coilv 71 jof Ithe field ff' switch- 46, thus permitting' this v s\'v itc h to* "Enjeu- Y andv thereby 'disconnectfthe field winclving 'from the source of excitation current.-

'fUnder' ordinary .conditions Ifwouldfso HippA j. 'lustthe frequency relay 4 1f aS'. .to impress the {,j. fullA voltage on the motorj when'. approz'ry teufel-rume; Per @entrai Synchronousm@ j to' thel armature winding. i f WhileI-:have shown'one' lstyle would :be closed at approximately ninety'per whenl the `motor isstarted vby .the pressing i loof the push but-ton 11 the motor will be "ibrou ht upf to synchronismlunder. the bestpossile `conditions for that motor 'for the particular load'which itis handling. The Winding, of the frequencywrelay 64: is

'd-'I energized by the secondarycurrent of trans-.

former 51 sothe action of -c losingthe 1nagnetic gap-'when the armature of' Athe relay is #drawn up will choke lthe secondary current andfthereby make the armature more easily SLU vreleased when the frequency of the induced `point 2.

"-While from" the nature ofthe methodand' means disclosed it is evident that the operav"-`5` tion will positive 'in nature, yet, if for 'any` reason the vfrequency relay'i 'failed to operate-between the points 3 and 5, it'vvould 'necessari-ly operate at thepoint 5, as there would be no induced current Whatever in "U the field Winding vat .that time; hence the polarized relay 68 would, in any event, be

' "actuatedvso that-even in case of failure of-A operation o f the frequency relay thefield.

current would be'thrown in.l `The push button 58 may be located ata distant point from the motor and theremay be a number of such buttons with their con# any one of theseV push buttons. This would allow the throw-out springs 53 to open the i switch I9, thus disconnectingthe motor'from the 'line. l L

I have'described my invention as applied be understood that the invention can be used' to good advantage with synchronous ma` prior to the application otfthe full voltage- I "relay and ene-style ofpolarizedirelay and a i' certain conventionall circuit, it is apparent flthat this' invention vcovers broadly' v 'any .-inethod or means'eontrolling any partor'all `of-thestarting. of a synchronous motor vvthrough a means controlled by the internal electrical condition of the'field winding, .and

the -main benefits of* my system,V

"current in the field .winding falls below the to va polyphase synchronous motor'but it will of frequency i Lcaaaea covers broadly an method or means by" Which the right the' instant the o fijeld is closed. 1

arity may be secured at The overload relays -100 are 4L :onneeted in I l the supply circuit in such a manner that the line current does netpass through these relays during -the -period when reduced voltage is vin'upressed on the motor armature.: This arrangement prevents the overload relayslOO from operating during the first part 'of-the starting period when the linecurrent is excessive."

. Whileh this invention has been described` as applied to its use with a synchronous -motor of the typewhich isstart'ed by first applying-reduced voltage, yet the motor starting system may be applied to synchronous mo-- tors of the full voltage t pe, i. e. synchronous motors which ma e started by impressing-' line voltagedirectly on the armature.

combination with a motor .ha-ving Val field wlnding, of a source of excitation for the field winding, automaticmeans' responsive to the electrical condition of the fieldwindfieldfwin'ding` of the" motor when it has reached a 'predetermined speed, said means 1. In a sys'temo'f the .type'described, the i I 'ingforsuppl-ying excitation current to the being adapted to 'open the field circuit when the motor speed falls below'a predetermined speed..

` '2. Ina system ofthe typedescribeda the combination-witha motor having a field lwinding,l of 'a source of excitation for the v field.- winding,`a `switch for connecting the tacts 1n` parallel, so-that the coilr 53 vand the switch 1 9 would loe-energized upon actuating field winding to the source of excitation,

and means'responsive fto the electrical condif tion of the field 'winding for closing said switch` when thev motor speed increases to. a predetermined value and for opening said certain" speed near synchronous speed.

" j 3. In a system of' the type described,the

combination with a motorhaving afield winding; and an armaturewinding, of means forapplyin'g voltage to the armature winding,-a switch for connecting'the field Winding of the motor to a source of excitation current, and means-responsive'to the electri-A cal conditionof the mai-n field winding for closing said switch when the motor speed `increases to a predetermined value and. 'for ,peningsaid switch when the motor speed falls below avcertain value.` 4. I n al system 0f the typev described, the combination with a. motor having an arma' ture winding and -a field `windingfof means for 'applying voltage.A to the armaturevwinding, automatic means responsive to `the elec winding 'when the motor has'- reached a predetermined speed, said .automatic means beswitch 'when the motor speed Afalls below a ing"adapted to open Itheiffiel'dfdircu'itf I" hen the motor-speed v'falls below. a predeter ined and automatic 'means associated-vvithlfftheH switch When'the "mio't'orspeedl fallsbelow a certain speed; .-f

y cal conditionof said field Winding for simotor` for supplying excitatio'nf l current to' the'field .winding 'when `the motor :has

reached apredeteri'i'iined speedand for open? ling the field circuit when the motor' speed falls belOWjacertain value, 'said automatidg means being exclusively responsive' to theA slip frequency 'of the 'current induced Iin the?. main field winding of the motor.l l

6. In af system fof the vtype described, the combinationwth a'motor havingl a'se'condary Winding, of asource of direct current, a resistance,means-arranged to short circuit the secondary w'indingthrough saidv resist-'- ance when the motor is starting, a 'switch' forconnect-ing said Winding to the source Off, direct current, and means responsive to the electrical condition` of 'said' winding for. simultaneously 1 opening .the short circuitthrough-said resistance and/closing -said Switch Whenthemotor has reached a piedetermined Vspeed and for opening said' 7.-In al system ofthe type described, the combination'with 'am'otor having an armature winding anda` field winding, of`mean`s for applying voltage 'to' the armature wind@ ing, a source vof direct current, al resistance, mea-ns arranged to sho-rt circuit the field winding` of the' motor thru 4said resistance when the motor is started,'aswitch for connecting saidwinding to the'source o fdirect current, and means responsive .to the electrimultane'ous'ly opening fthe shorty circuit thru said resistance-and closing said switch wh'en the motor has vreached a predetermined speed and-for opening-said vswitch when the motor, speed falls below a certain Value.

8. I a system of the -type described', the combinat1onw1th a motor havingan ,armature Winding and a? field winding, 0f means for applying voltage to the armature winding, a source of direct current, a resistance, a two-positionswitch arranged so that in one position 'it connects said resistance across the field winding and in the other position Iit' connects the source of direct current 'to the field winding, and means responsiveto the' electrical condition ofssaid field winding for .operatifq-said switch to disconnect said resista e om'thefield Win'dingand to'connect son' ce `o fdirect current to the field winding when the moto'rhas reached a pre-v determined speed.A

n 9. In a system` of the type described, the

combination lWith a motor having' an 'armag ture winding.. and a field winding, of means position it connects isa-id resistance aci'os's lthe .afield windingiand in the other position itcon'nect'sthe source of direct'current to the field winding,f,and Omeans responsive to' the electrical 'condition of said field Winding forI nc 'iperatin g said switch to disconnect said resi-stance from 1the field windingsto connect' vtheasource of 4direct,current to the field `Wind- ,ingiwhen t-he'motor has reached. a predeter 4mined speed, `and to disconnect the source ofdirect .current from the field winding and connect the resistance thereto when the "mo- W10. In 'meansfor startingfa' synchronous g ture and' a fieldwinding, of .a .source of excitationfor'the field Winding, means for applying voltageto the .armature of the motor,

'and .automatic means associated with the motor f'or supplying excitation current to the field winding when them'otonhas reached a predetermined speedhsaid 'automatic means comprising a field switch` and a polarized frequency'relay responsive to the frequency of the induced -current in the' main field winding, said relaybeing connected in circuit witli said field winding at all times.

12. In asystem of 'the type described, the

"combination with annotor having a field wrnding and an armature winding, of 'means for-applying voltage to the armature winding, and automatic means associated' with the motor .for supplying excitation' 'current to the field windingwhen the motor has reached a predetermined speed, said automatic means comprising a field switch and a polarized lfrequency relay` responsive to the frequency of the induced currentiii the main field winding, said relay being in operative connection withl said field winding at `all times. 13. In a system of the type described, the combination with amotor having an armaturewinding an'd'a field Winding, of means for-applying voltageto the armature of the, motor, and automatic means responsive to the electrical condition of the field vwinding for supplying excitation 'current tothe field winding when tlie'motor has reaclied'a predetermined speed, said automatic means be-. ing'inoperable until voltage has been ap- 14. In a system of the type descrihedgthe combination with a motor having an armature and a field winding, of a'souice of excitation :for the field winding, means including a switch for applying voltage to the armature of the motor, and 'automatic means` responsive to the electrical condition of the field winding for lsupply-ing excitation current to the field winding of the-motor v'when combination witha motor 'h a'ving an' armature Winding and a field windxng,` of means the motor has reached apredetermined speed; said automatic means being inoperable until voltage has been applied'to the armature, and said automatic means being adapted to`i open' -the field circuit when 'the motor speed falls below the predetermined'speed.

15. In a system of the type described, the

f or applying voltage to the armature of the motor, said means including a switch cont-rolled circuit and an electromagneticl switch having a coil energized by said circuit, and automatic means res onsive to the electrical condition of the fiel winding for supplying excitation current to the' field yvinding when the motor has reached. a predetermined speed, said automatic means being inoperable until voltage has been applied to the armature, and said automatic means being adapted to open the field circuit when the motor f 'speed falls below a predetermined value.

16. In a systemof` the type described, the combination with a motor having a field winding of a reacta'nce connected in the field circuit, a V:frequency relay having a magnetizing coil connected across'the reactance, and a field'switch adapted to be closed by said relay when the frequency of the induced current in the field winding has decreased to' a predetermined value, the reactance f being connected in said field circuit at all times.

17. In a system of the type described, the combination with a motor having a field winding of' a source of excitation for'the field winding, areactance connected in 'series with the field winding of the motor,4 .a resistance connected across the .field winding andthe reactance during the starting of the motor, a frequency relay connected across said reactance and responsive to the frequency of the induced current in the field' winding, and a switchoperable by said frequency relay 'to supply excitation -current to the field winding when the frequency of the induced current has decreased to a predetermined value, said' switch having means for' opening the circuitl of the resistance connected tothefield winding and the reactan'ce.

without disconnecting the reactance from the biiiation with .an alternating current motor having a field circuit vthat is energized by the motor when tlie latter operates below synchronous speed and means for establishing starting and running primary 'connections for said motor, of means for-controlling'the establishing of said running connectioii in accordance with the'value of the current traversingfsaid field, circuit. 19.- f llie starting system for synchronous motors, comprising tlieiconibination with a .motor of 4means includingaswitch for applying reduced voltage to 'the armature and means normally connected to the main field winding at all times and exclusively responsive to the induced current in the main field winding for automatically applying full voltage to .thel armatureatter the moto'r has attained a .predetermined speed. l

20. In" a motor control system, the combination 'with a mot'or having a primary circuit and an exciting circuit-and a source of energy, of means for preventing the connection of said source lto said primary circuit to apply normal voltage thereto when the current traversing a. portion of said exciting circuit exceeds a predetermined value.

21. In a motor control system.l the combi- I nation with an alternating current motor having a field circuit that is energized by the motor when the latter operates below Synchronous speed and means foiestablishing starting and running primary connections for said motor, of -means operable only while the starting connections ar-e maintained for controlling the establishing of said running connection in accordance withv the value ot the current transversing said field circuit.

.22. In a motor control system, the combination with asynchronous motor having a tieldmagnetwinding and an armature winding` and switching means for establishing' starting and running connections for Saidarmature winding, of means comprissaid' starting connections, and the opening of said starting connections and the establishing of said'runnnig connections when the alternating lci'irreriti .-traversing said fieldmagnet winding falls below a "predeterniined value.

23. In a motor nation with a synchronous motor having a field `magnet winding. et means forA controlling the establishingot starting and running primary connections therefor, said means comprising a switch embodying electromagnetic means for preventing the closing of said switch-so long as the current trav-v ersing' said winding exceeds a predetercontrol system, the combimined value While the starting connections are maintained.

i 24'. In a system ,ofyelectrical distribution, a source of alternating current, a synchronous dynamo-electric machine' adaptedto be connected to said source, switchingmeans for controlling the connection of said in achine to said soince,'and'means responsive to the slip frequency of said machine for con# trolling said switchingI means, the means)` responsive to the slip fr-cquency of .the inachine being connected in a' 4closed circuit `at all times.

25. The starting syst'em for s y'fnchronous i5 motors, comprising the combination ".With-'a inotoi'cf means including' a switch for applying reduced voltage to the armature, and` iii-cans normally connected to the .main field winding at .all timesand excl'usiyely -rezo sponsive to the frequency of the induced current in the main field yw'fiiiding for ,automaticallyapplying fullvoltlage to the arma'- ture after the motor has attained agpredes termined speed. A 26. A starting system' for syncl'ironous motors, comprising the combination with a. motor ofa double 'throw line switch havlfor actuating said first named electromagnetic l .i

means, and-means controlled by the internal "i i electrical.' condition of the field,` Winding" of the 'motor being gstartedf. for actuating l said second named elee'tromagnetic'dev-ice, a

source of lield excitation current anda frequency. relay arranged so that field excitaf' l I tion' current` mayk be 4applied to -the fieldf. t' "i winding of the 'motor vWhe-n the lfrequency of lthe induced current inthe field winding.

falls below/.apifedetermine'd iate. A i 29. 1n means for.startinga synchronous lmotor the combination of v'a two-wayv main line switch, an adjustabletransformer, elec- .tromagnetic means for `closing theswi'tchin one direction, asecond electromagi'ietic.

means forclcsing the switch in the 'opposite directioinffa push button, means controlled by said push button for energizing said first named electromagnetic' means, 'an electrical' circuit*connecting the motor to be started to a low1 voltage tap onsaid transformer' whenv said switch is thrownl in -t-s first .namedy position, means controlled by the internal electrical condition of the field winding of the motor to be started for throwing' said switch to its second named position, a

ing one set of teri'ninals connected directly source of fieldexcitation current, means for to the motor, a source'ofreduced voltage '30 connected to another set ofterininals of said switch andto said` motor, meansA for closing said switch to4 connect the line to the source of reduced voltage whereby' reduced voltage .is applied tothe motor, and 'mea-ns normally Iconnected to the main 'field winding of the motor at all times and exclusively responsive'tor'current induced -in the main field winding, for auton'iatically reversing said lincvswitch, whereby full line voltage is ap-l 40 'plied to the moton 27. A. starting system for synchronous= motors, comprising the combination with a motor of a double throw-line switch .having one set ofterminals connected directly to the inotor,a source of reduced voltage connected to another set ofterminals of said switch' and to said` motor, means for closv'ing said switch `to connect the line to the source of reduced voltage whereby reduced 50 voltage, is applied to theqmotorl'ineans normally connected .to the vmain field winding of the 'motorat all times and directly re? sponsive to current induced in the main field winding, for automatically reversing. said line switchl` whereby `full line-voltage is applied to the motor, and means for automatically opening said line switchwhen said reversing means is inoperative.

28. ln means for starting a synchronous motor the combination with the motor of a two-way line switch, electromagnetic means for closing said switch inl one direction, -a second electromavnetic means for closing said main line switch. in the opposite direction, means including circuit closing device relay having amagnetiziiig coil connected across the secondary winding of the transformer and .af field switch adapted to be closed ,by said relay when the frequency of the induced current in the field winding has decreased to a predetermined value, the said transformer being connected in the field circuit at. al1 times.

`3l. In a system of the type described, the

lli)

combination with a inotorhn'ving an armature and a field winding, of means, for applying voltage 4 to the armature, a transformer haring its primary,winding conneeted in series with the field winding of the motor, a resistance connected across the field winding and the primary winding of the transformer during the starting of the motor,`a frequency relay connected across the secondary winding of said transformer and responsive'to the frequency of the induced current in the field winding, and a switclicontrolled by said frequency relay to supply excitation current to the field winding when the frequency of the induced cnrient has decreased to a predetermined value, i

said switch having` means forcpening the circuit of the resistance connected to the field winding, and the primary..winding o f the transformer without disconnecting the transformerf'rointhe field circuit'. V B2-The combination with asynchronous electric/. motor having a primary Winding and a field magnet winding,l cfa circuit including -said eld.. -magnet `Winding. and

means inductivelyf related to said circuit' for. controlling the' circuit ofsaid-primary'wind- The combination-with a synchronous alternating -current motori having a primary circuit Ofi sind, iii-id magnet winding, Said incans coinprising'arelay' having' a' coil in circuit with said"' Wmdiiig;l andy 'a second coil i-nductively related to thefrst named' coil.-

34.' In a `motor.cojntrol system, tl'iefcombination with a synchronousinotor' having a field 'magnet winding-fof means `for control-y ling the'establishing vofs'tart'ing[and running primary connections'- there'for, ,said means comprising a switchsembodying -a closing coil .and a lockout-coil 'that is energized 'fin '-ac`cordance with thc n value, 'of :the current traversings'aid winding, saidwlock-v witli asynchronous l motor having afield inagnet "Winding, andstarting and running connections forjsaid motor, of a switch controlled-i-n accordance with the value of the f current -trainersing- "sa,id windingl for conj trolhngthe'circuit of said winding, as witch for effecting vthe transfer .from starting connections to running connections anda relay' having an aetuatingcoilm circuit with said.

- Winding for controlling the second named switch.

36. Ina motor control system, the combi-r nation with `a synchronous motor having a field magnet winding that is self-excited when the inotoroperates below synchronous speed, separate means for energizing Said winding and means for applying voltages of differenty valuesv to said motor :for starting and for normal operation, of means for con- 'trolling the value of' the voltage applied to said motor and-the connection of said winding to 'said energizing means in accordance with the value of the ourrent'traversing said Winding.- i

f nation with an alternating' :current motor ing mechanism for establishing main starthaving a field magnet winding and'switching and running connections :for said motor, of means for energizing said-Winding during normal operationof said motor, and

automatic means for effecting the establishing of said running connections and the connection of said winding to said energiz- 'ing means when the current traversing said4 Winding duringlthe starting operation falls .tion ,of said machine and the connection of' 'said machine to said source.` 39.- In a'motor control systeii,-the combination with a motor, a field circuit therefor ,and means for energizing 'said circuit, of a source. of energy. at low voltagefor starting said motor and a source`of energy at high voltage for normally lsupplying said motor, and means 'for preventingthe connection of said iiergizingmeans to said. field circuit .andof sa-id'niotor to said source of' energy at highvolta-ge when the current traversing a potion' of said field circuit exceeds a predterminedyalucg- 440g-In' a motor control-system, the combivi`fia t 'ion"with an alternating current motor having-*afield,magnet winding and switchv of means for energizing said winding dur- Ina -motor startenthe combination inggnornial operation/of said motor, and

Afautomatic mean's" for`effect ing the establish- A'-ingof said running connections and the coninaction ofsaid windingto said energizing 'means' when'th-e current traversing said nation with an `alternating current motor hav-ing a field magnet winding and switching-mechanism forestablishing main starting and running connections' for saidv motor,

of meansfor energizing said windinv during normal operation of said motoigfand automatic means for effecting the establish- 'ing of saidiunning connections and the connection of said winding to said energizing. means when the current traversing said -windiiig during the starting operation falls below a predetermined value, said automatic -ineans comprising a switch having a closing i -coil and a lockoutcoil that is in circuit with 37. In a motor control system, the combi..

said field magnet winding at all times.

42. In a motor control system, the.combi nation with a synchronous motor having a field magnet winding that is self-excited iis when the motor operates below synchronous speed, separate means for energizing said Winding and means rfor applying voltages of different values to said motor for starting and for normal operation, of means for controlling the value of the voltage applied to said motor and the connection of said winding to said energizing means in accordance with the value of the current traversing said winding, said means comprising a switch having a lockout coil' in circuit with said field magnet winding.

43. In a motor control system, the' combination with a synchronous motor havinga field magnet winding that is self-excited when the motor operates below synchronous speed7 separate means `for energizing said winding and means for applying :voltages of different values to lsaid-motor for starting and for normal operation, of means for controlling the value of the voltage" applied to said motor and the connection of said winding to said energizing means in accordance with the value o the. current traversing said winding, said means comprising a switch having a closing coil and a lockout coil that retains said switch in-open position so long as said winding is self-excited beyond a predetermined degree. s

'44. The method of startinga synchronous Inotor comprising the application o'f low voltage to the motor andthereafter applying the full voltage of the supply circuit tothe motor at a time when the frequency of the induced field current is a` predetermined value and applying the field excitation current to the field winding at a time when the frequency of the induced field current is a rcontrolling thev value of the voltage applied windin 4Z. T e method of starting a synchronous' ing` the field excitation current to the speed, separate means forenergizing ,saidf of differentvalii'es to said' motor for starting ancifornormal operation, of means ,for

to said motor` andthe connection o said Winding to said energized means in accordance .with vthe electrical conditionA of said motor comprising the application of low `se?v winding and means for applying voltages voltage to the motor and thereafter applying the full voltage of the supply circuit to l the motor at a time when the induced field 'current is a predetermined value and ap lyeld winding at a time when the frequency of the induced field current is a predetermined value and at the instantof a predetermined direction of field current. v y v l 48. rlhe method of starting a synchronous motor comprising the yapplication of a low voltage theretoythereafter applying the full voltage of the supply circuit to the motor at a time whenthe frequency of the induced field current is a predetermined value and applying the-excitation current to the field windingl in such a direction and at such a time as to bring the motor into synchronism.

49. 'ihemethod of starting a synchronous motor which consists in supplying the motor with aredlld voltage and after the motor has attained a considerable percentage of pulsation of the said induced synchronous speedv and the frequency of the induced field current has dropped to a predetermined rate, applying the full voltage of the supply circuitr to the motor and when the motor has attained substantially syn u chronous speed and the frequency of .the induced field current is low, applying the field excitation current tothe field Winding at such an instant with respect to the direction of pulsation of the induced field cur-A rent that the field excitation current will tend to at once bring the motorA into synchronism.

CHARLES TRUMAN rima/inn. 

